2012 aquatic macrophyte survey of Otsego Lake

D. McShane1

and K. Mehigan2

INTRODUCTION

Otsego Lake was formed by the over deepening of the headwaters of the Susquehanna River by glaciation (Harman et al. 1997). Otsego Lake contains appreciable nutrient quantities from both cultural and natural sources, yet remains fairly oligotrophic in nature. Narrow shorelines combine with considerable depth to create a limited phototrophic zone (Harman et al. 1997). Despite the restricted area plants can grow, Lake Otsego is able to possess a fairly diverse range of aquatic macrophytes. Aquatic macrophyte community studies in Lake Otsego began when Muenscher (1936) completed an extensive survey on the plants in 1935. Studies conducted by Harman and Doane (1970) in 1969 followed Muenscher’s work. Fluctuations in plant species abundance and distribution have been recorded over time (Harman et al. 1997, Harman and Doane 1970), with the 2005 survey showing significant variation from its 1935 counterpart (Harman 2005). When Muenscher originally conducted the study, 23 different macrophyte species were noted in Lake Otsego (Harman et al. 1997). As of 2005, there were 24 species of plant present (Harman 2005). Since 1935, 6 species of plant have been lost from Otsego Lake while 5 other species have been introduced. The abundance of each species continues to vary from study to study. Plant distributions were again mapped in 2012. This effort was primarily to evaluate the influences to the plant community by the recent discovery of two additional exotic invasive species in Lake Otsego. Zebra mussels (Dressina polymorpha) were first documented in 2007 and considered abundant by spring 2010 (Albright and Zaengle 2012). The resultant increases in water clarity (i.e., Waterfield and Albright 2012) were expected to have had substantial influences on plant communities and their distributions. Second, the macroalga starry stonewort (Nitellopsis obtusa) was first noted in Otsego lake in 2010 (Harman 2010) and its expansion has been anecdotally noted. It has been regarded as an aggressive invader elsewhere (Pullman and Crawford 2010, Albright and waterfield 2012).

The focus of this project is to perform a study similar to those of 1935 (Muenscher 1936), 1969 (Harman and Doane 1970), 1976 (Brady and Lamb 1977), 1986 (Dayton and Swift 1987). 1993 (Harman 1994) and 2005 (Harman 2006) focusing on relative abundance and percent cover of plant species at specific locations around Lake Otsego. The techniques employed included PIRTRAM (Point Induced Rake Toss Relative Abundance Method; Lord and Johnson 2006) and in-water observations via snorkeling gear. These techniques allow for a rapid, yet thorough assessment of the lake.

1 SUNY Oneonta Biology Department Intern, summer 2012. Present affiliation: SUNY Oneonta. 2 Otsego County Conservation Association Intern, summer 2012. Present affiliation: SUNY Oneonta.

METHODS

We visited 54 sample sites on Otsego Lake, along the shore and around Sunken Island over the summer of 2012 (Figure 1). Sites were marked on a GPS (Table 1) and returned to within 10m of the original site over the course of the summer. Sites were selected based upon lake geography and the previous survey locations (Harman & Doane, 1970). At each site we determined the relative abundance and percent cover of each plant species using two methods; PIRTRAM (Lord and Johnson 2006; see below) and snorkeling. We sampled using the PIRTRAM three times during the summer, 7 June, 9 July and 28 July. Snorkeling observations were made twice during the summer, on 21 June and 9 July.

Table 1. GPS coordinates of all 54 sample sites located on Lake Otsego in the summer of 2012. See Figure 1 for site locations.

Site Approximate GPS location Site Approximate GPS location 1 42°43'2.00"N 74°55'29.97"W 28 42°44'23.00"N 74°54'35.39"W 2 42°42'57.61"N 74°55'27.97"W 29 42°44'9.51"N 74°54'47.70"W 3 42°42'49.94"N 74°55'24.61"W 30 42°44'3.94"N 74°54'50.51"W 4 42°42'45.50"N 74°55'24.48"W 31 42°43'44.42"N 74°55'1.96"W 5 42°42'34.47"N 74°55'25.94"W 32 42°43'29.77"N 74°55'15.06"W 6 42°42'19.31"N 74°55'28.60"W 33 42°43'25.96"N 74°55'16.92"W 7 42°42'14.69"N 74°55'26.57"W 34 42°47'29.16"N 74°53'49.41"W 8 42°42'6.70"N 74°55'14.07"W 35 42°47'42.84"N 74°53'27.92"W 9 42°42'10.76"N 74°54'59.48"W 36 42°47'48.20"N 74°53'28.99"W 10 42°42'19.77"N 74°54'53.61"W 37 42°47'47.38"N 74°53'33.38"W 11 42°42'39.12"N 74°54'47.56"W 38 42°48'5.67"N 74°53'59.12"W 12 42°43'1.52"N 74°54'36.86"W 39 42°48'15.14"N 74°53'53.53"W 13 42°43'20.94"N 74°54'28.93"W 40 42°48'27.42"N 74°53'44.58"W 14 42°43'35.61"N 74°54'23.56"W 41 42°48'38.01"N 74°53'49.98"W 15 42°43'44.84"N 74°54'17.14"W 42 42°48'41.63"N 74°53'27.23"W 16 42°43'57.34"N 74°54'1.30"W 43 42°48'34.92"N 74°53'0.24"W 17 42°44'34.57"N 74°53'38.19"W 44 42°48'17.68"N 74°52'59.45"W 18 42°45'11.23"N 74°53'19.01"W 45 42°48'5.71"N 74°52'59.03"W 19 42°46'10.28"N 74°52'57.65"W 46 42°47'27.03"N 74°52'45.39"W 20 42°46'17.22"N 74°52'55.65"W 47 42°47'29.01"N 74°52'26.38"W 21 42°45'50.81"N 74°53'58.70"W 48 42°47'14.43"N 74°52'8.38"W 22 42°45'19.76"N 74°54'9.75"W 49 42°46'52.94"N 74°52'26.92"W 23 42°45'11.80"N 74°54'15.20"W 50 42°46'37.60"N 74°52'44.89"W 24 42°44'58.79"N 74°54'18.29"W 51 42°46'2.88"N 74°53'59.65"W 25 42°44'49.11"N 74°54'20.91"W 52 42°46'35.38"N 74°53'58.50"W 26 42°44'39.91"N 74°54'24.94"W 53 42°46'39.61"N 74°53'56.64"W 27 42°44'35.22"N 74°54'25.41"W 54 42°47'11.92"N 74°53'50.40"W

PIRTRAM

PIRTRAM is an efficient method used to analyze relative abundance amongst submerged aquatic plant communities. PIRTRAM is able to determine presence/absence, frequency and relative abundance (Lord, 2006). While evaluating the plant community of macrophytes of Lake Moraine, the PIRTRAM was compared to the biomass method (Harman et al. 2009). PIRTRAM was found to underestimate biomass 80% of the time compared to the actual plant dry weight determinations, but it tended to describe the communities with relative consistence.

For the PIRTRAM, two garden rake heads were welded back to back to form a double sided rake; this was connected to a 10 m long nylon cord. The rake was tossed, and when settled, retrieved slowly. Sampling was done in triplicate at each site with each throw tossed in a different direction. Retrieved plants were then separated, identified by species and assigned an abundance category, as outlined in Table 2. Biomass range estimates (g/m2) were assigned for each of the above abundance categories. The midpoint of each category was used for data analysis. The total plant biomass at each site was calculated as the mean biomass for each species (based on three tosses) at each site. The method was taken from the “The State of Canadarago Lake” (Albright and Waterfield 2012). We used PIRTRAM data to standardize how visual surveys were interpreted.

Table 2. Biomass range estimate of plants in g/m2, by species, utilized in the rake toss (PIRTRAM) method. Mid values were used as estimates in the following tables and figures.

Abundance Category Field Measure Total Dry weight Range (g/m2) Midpoint (g/m2)"Z"= no plants Nothing 0 0"T"= trace plants Fingerful 0-2.0 1"S"= sparse plants Handful 2.0-140 71"M"= medium plants Rakeful 140-230 185"D"= dense plants Can't bring in boat 230-450 340

SNORKLEING

We utilized snorkeling equipment at each sample site to visually describe the macrophyte species at all canopy levels. Snorkeling allowed us to estimate percent coverage of a species over larger areas and allowed for data comparison between the relative abundance data provided by the PIRTRAM. At each site we entered the water and began observing the area in a zigzag pattern that lead from the boat to the shoreline. Plant species were identified in the water and percent cover was estimated for each species at that location. If a sample could not be identified in the water, the specimen’s percent cover was noted and a sample was retrieved for a more comprehensive analysis referencing Borman et al (1997). We returned to the boat when our pattern was complete and recorded our estimates in a log book. Percent cover was reviewed in conjunction with PIRTRAM data to help estimate relative abundance of macrophyte species.

Figure 1. Otsego Lake, New York, showing sites sampled for aquatic macrophytes, summer 2012. See Table 1 for site coordinates.

RESULTS

Table 3 represents the relative abundance ranking for all plant species found in 2012. Rankings are based on PIRTRAM data in conjunction with visual surveys. Tables 4 through 6 show the complete PIRTRAM data set for all 54 sites over the 11 June, 21 June and 9 July sampling periods. An “O” denotes a species that was observed but not collected.

Figures 2 and 3 provide distribution maps of nuisance invasive macrophytes on 21 June and 9 July sampling dates, respectively. Plants included Potamogeton crispus, Najas guadalupensis, Myriophyllum Spicatum and Nitellopsis obtusa. (Note that distribution maps were not created for the 11 June survey as snorkeling efforts were not employed then. PITRAM only data were not expected to provide comparable distributions). Figures 4-9 show distribution maps of native plant species on the two sampling dates. Multiple maps for each date were generated so that the legends were more readable and so the map symbols were more easily distinguished. Figures 4 and 5 show the distribution of Vallisneria americana, P. pusillus, P. illinoensis, Megalodonta becki and P. amplifolius on 21 June and 9 July, respectively. Figures 6 and 7 show the distribution of elodea Canadensis, Zosterella dubia, Ceratophyllum demersum, P. pectinatus and Chara vulgaris on 21 June and 9 July, respectively. Figures 8 and 9 show the distribution of Nitella flexilis, P. praelongus, P. richardsonii, Najas flexilis, P. gramineus. P. zosteriformis and Ranunculus aquatilis on 21 June and 9 July, respectively.

Aside from the species summarized in the included Tables and Figures, a single specimen of water chestnut (Trapa natans) was collected, though not as part of this study. It was a small plant, <20 cm, growing directly from a nut within 1 m of the public landing dock in Springfield (Albright 2012a).

Table 3. Presence, absence and abundance of aquatic macrophytes in Lake Otsego (modified from Harman, 2005). * Note: Myriophyllum spicatum was misidentified as M. sibiricum in the 1986 study. Bold species are non-native pests. From Muenscher (1936); Harman and Doane (1970); Brady and Lamb (1977); Dayton and Swift (1987); Harman (1994) and Harman (2006).

Abundance Species 1935 1969 1976 1986 1993 2005 2012

Ceratophyllum demersum A F C C F C C Elodea canadensis A C F F F F F Najas flexilis A A A F C R C Nymphaea odorata F C C F C C C Nuphar variegatum F C F C C C C Potamogeton pectinalus C C A C F A A Potamogeton praelongus C F C C C C C Potamogeton pusillus F F A C C C R Potamogeton zosteriformis C R F C C C C Ranunculus trichophyllus C F F F C C C Vallisneria americana C C C C C C C Zosterella dubia A A A C C F A Potamogeton epihydrus R - - - - - - Potamogeton foliosus R - - - - - - Potamogeton friesii C - - - - - - Potamogeton natans F R R - R R - Potamogeton nodosus - R R - R - - Myriophyllum sibiricum C F F C* R - - Potamogeton amplifolius F R R - C F F Potamogeton gramineus A C C - R R R Potamogeton illinoensis - F F F C C C Potamogeton richardsonii C F C - C R C Megalodonta beckii C F F - C C C Potamogeton crispus - A A F F F F Najas guadalupensis - - - - - C F Myriophyllum spicatum - - - - A A C

Macroalgae Chara vulgaris A A A C F F F Nitella flexilis A C A F F F F Nitellopsis obtusa - - - - - - C Total Number 23 23 23 17 24 23 23 A = Abundant, F= Frequent, C = Common, R = Rare

Species 11-Jun-12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

Potamogeton amplifolius

Potamogeton crispus 185 340 1 1 71 1 1 1 1 71 185 71

Potamogeton gramineus 1

Potamogeton illinoensis 1 1 71 1 1 1

Potamogeton pectinalus 1 1 71 1 1

Potamogeton praelongus

Potamogeton pusillus

Potamogeton richardsonii

Potamogeton zosteriformis 1

Najas guadalupensis

Najas flexilis

Vallisneria americana 71 1

Zosterella dubia 1 185 71 1 1 71 185 1 71

Ceratophyllum demersum 71 1 1 1 1 1

Nymphaea odorata O

Nuphar variegatum O O O

Elodea canadensis 185 1 1 1 1 71

Ranunculus aquatilis

Myriophyllum spicatum

Megalodonta beckii

Chara vulgaris 71 185 71 185 71 1 71 1 71 71 1 1 1

Nitella flexilis

Nitellopsis obtusa

Table 4. Summary of estimated biomass (g/m2) of submergent aquatic macrophytes collected in Lake Otsego using PIRTRAM on 11 June 2012. Values provided are g/m2 mean midpoint values (see Table 2) of each site. An “O” signifies species that were observed but not collected. See figure 1 for site locations.

Species 11-Jun-12 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

Potamogeton amplifolius 1 1

Potamogeton crispus 185 185 71 1 185 1 71 71 71 1 185 71

Potamogeton gramineus

Potamogeton illinoensis 1

Potamogeton pectinalus 1 1 1 1 71 71 1 185

Potamogeton praelongus 71

Potamogeton pusillus

Potamogeton richardsonii

Potamogeton zosteriformis

Najas guadalupensis

Najas flexilis

Vallisneria americana 1 1 1

Zosterella dubia 71 340 1 1 1 185 1 185 71 71 1 185

Ceratophyllum demersum 71 1 1 71 1 1 1 1

Nymphaea odorata O O O O O O

Nuphar variegatum O O O O O O O

Elodea canadensis 1 71 1 1 1 1 1 185 71 1 185

Ranunculus aquatilis

Myriophyllum spicatum 1 1

Megalodonta beckii

Chara vulgaris 71 1 185 1 71 1

Nitella flexilis 71 185

Nitellopsis obtusa

Table 4. (cont.) Summary of estimated biomass (g/m2) of submergent aquatic macrophytes collected in Lake Otsego using PIRTRAM on 11 June 2012. Values provided are g/m2 mean midpoint values (see Table 2) of 3 tosses. An “O” signifies species that were observed but not collected. See figure 1 for site locations.

Species 28-Jun-12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

Potamogeton amplifolius 1 1 1

Potamogeton crispus 1 71 71 1 1 1 1 1 1 1 1 71

Potamogeton gramineus

Potamogeton illinoensis 1

Potamogeton pectinalus 71 1 1 71 1 1 71 1

Potamogeton praelongus 1

Potamogeton pusillus

Potamogeton richardsonii 1

Potamogeton zosteriformis 1 1 1 1

Najas guadalupensis 1 1 1 1 1

Najas flexilis 1

Vallisneria americana 1 1 1 1 1 1 71 1 1 1 1 1

Zosterella dubia 71 71 71 71 1 71 71 71 71 1 71 1

Ceratophyllum demersum 1

Nymphaea odorata O

Nuphar variegatum O O

Elodea canadensis 1 71 1 1 1 1 71

Ranunculus aquatilis 71 1

Myriophyllum spicatum 1 1

Megalodonta beckii

Chara vulgaris 71 1 71 71 1 71 1 1 1 71 1 1

Nitella flexilis 71 1 1 1

Nitellopsis obtusa

Table 5. Summary of estimated biomass (g/m2) of submergent aquatic macrophytes collected in Lake Otsego using PIRTRAM on 28 June 2012. Values provided are g/m2 mean midpoint values (see Table 2) of 3 tosses. An “O” signifies species that were observed but not collected. See figure 1 for site locations.

Species 28-Jun-12 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

Potamogeton amplifolius 1 1 1

Potamogeton crispus 1 71 1 71 71 1 1 1 1 1 185

Potamogeton gramineus

Potamogeton illinoensis 1

Potamogeton pectinalus 1 1 1 1 1 1 71 1 1 1

Potamogeton praelongus 71 1

Potamogeton pusillus

Potamogeton richardsonii

Potamogeton zosteriformis 1 1

Najas guadalupensis 1 1 1

Najas flexilis 1 1

Vallisneria americana 1 1 1 1 1 1 1 1 1 1 1

Zosterella dubia 1 1 1 71 1 1 71 1 1

Ceratophyllum demersum 71 1 1 71

Nymphaea odorata O O O O O O

Nuphar variegatum O O O O O O O

Elodea canadensis 1 1 71 1 1 71 1 1 1 1 1 1 1 1 71 185

Ranunculus aquatilis

Myriophyllum spicatum 1 1 1

Megalodonta beckii 1

Chara vulgaris 1 1 1 1 1 71 1 1 1 1

Nitella flexilis 1 1 71 71

Nitellopsis obtusa

Table 5 (cont.). Summary of estimated biomass (g/m2) of submergent aquatic macrophytes collected in Lake Otsego using PIRTRAM on 28 June 2012. Values provided are g/m2 mean midpoint values (see Table 2) of 3 tosses. An “O” signifies species that were observed but not collected. See figure 1 for site locations.

Species 9-Jul-12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

Potamogeton amplifolius 1

Potamogeton crispus

1

1

Potamogeton gramineus

1

24

Potamogeton illinoensis

Potamogeton pectinalus

1

1

Potamogeton praelongus

1 48

1 1 1

1

1 1 24 1

Potamogeton pusillus

1

1

Potamogeton richardsonii

1

Potamogeton zosteriformis

1

1

Najas guadalupensis

1

1

Najas flexilis

1

1

1

1

1

Vallisneria americana

24

24

1

Zosterella dubia 1 24 24

24

1

1

147 1

1 48

Ceratophyllum demersum

71

1 1 1

24

24

1

1 123

Nymphaea odorata

O

1

48

62

Nuphar variegatum

O

O O

Elodea canadensis

1 1

Ranunculus aquatilis

24

1 1

1 1 1

1

288

24

Myriophyllum spicatum 24

48

48

Megalodonta beckii

1

Chara vulgaris 48 1 1 62

Nitella flexilis

1 24

1 71 24

24

85 85

1

1

Nitellopsis obtusa

24

48 1 24

1

1

1

62

Table 6. Summary of estimated biomass (g/m2) of submergent aquatic macrophytes collected in Lake Otsego using PIRTRAM on 9 July 2012. Values provided are g/m2 mean midpoint values (see Table 2) of 3 tosses. An “O” signifies species that were observed but not collected. See figure 1 for site locations.

Species 9-Jul-12 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

Potamogeton amplifolius Potamogeton crispus 1 1 1 1 Potamogeton gramineus 1 Potamogeton illinoensis 1 24 Potamogeton pectinalus 24 24 1 24 1 24 Potamogeton praelongus 62 1 1 1 1 Potamogeton pusillus Potamogeton richardsonii Potamogeton zosteriformis Najas guadalupensis 1 24 Najas flexilis Vallisneria americana 1 24 62 24 1 86 1 1 48 1 Zosterella dubia 1 1 1 24 24 1 1 24 340 48 1 Ceratophyllum demersum 109 71 1 62 48 1 24 62 Nymphaea odorata O O O O O O Nuphar variegatum O O O O O O Elodea canadensis 62 48 1 1 1 1 1 24 Ranunculus aquatilis 24 24 24 1 Myriophyllum spicatum Megalodonta beckii Chara vulgaris 71 1 24 1 Nitella flexilis 24 24 1 85 1 71 24 Nitellopsis obtusa 24 48

Table 6 (cont.). Summary of estimated biomass (g/m2) of submergent aquatic macrophytes collected in Lake Otsego using PIRTRAM on 9 July 2012. Values provided are g/m2 mean midpoint values (see Table 2) of 3 tosses. An “O” signifies species that were observed but not collected. See figure 1 for site locations.

(% cover)

Figure 2. Percent cover of the nuisance invasive macrophytes at each site location, 21 June 2012.

6/21/2012

Figure 3. Percent cover of nuisance invasive macrophytes at each site location, 9 July 2012.

7/9/2012

(% cover)

Figure 4. Percent cover of native macrophytes found in Otsego Lake, 21 June 2012.

6/21/2012 (% cover)

Figure 5. Percent cover of native macrophytes found in Otsego Lake, 9 July 2012.

7/9/2012

(% cover)

Figure 6. Percent cover of native macrophytes found in Otsego Lake, 21 June 2012.

6/21/2012

(% cover)

Figure 7. Percent cover of native macrophytes found in Otsego Lake, 9 July 2012.

7/9/2012 (% cover)

Figure 8. Percent cover of native macrophytes found in Otsego Lake, 21 June 2012.

6/21/2012 (% cover)

Figure 9. Percent cover of native macrophytes found in Otsego Lake 9 July 2012.

(% cover) 7/9/2012

DISCUSSION

The aquatic plant communities and the relative abundance of most species of plants in Otsego Lake over the summer of 2012 were similar to those described in other recent studies. Of the 23 species found in the 2005 study, 22 were also documented in 2012. Potamogeton natans (floating-leaf pondweed) and P. nosodus (long-leaf pondweed) were not observed during the 2012 survey. Perhaps most notable finding relates to increases in the density of starry stonewort (Nitellopsis obtusa). It was first observed in 2010 (Harman 2010) and has become abundant and well established, forming dense beds in the understory at the northern end of the lake.

Six abundance rankings have been changed since the 2005 study. Those species are P. pusillus (small pondweed), M. spicatum (Eurasian milfoil), Najas guadalupensis (southern niad), Najas flexilis (slender niad), Zosterella dubia (water stargrass), and P. richardsonii (clasping-leaf pondweed). Potamogeton pusillus has become increasingly rare around the lake, never being collected using the rake toss at any location and never being observed at over 10% cover for any location. Potamogeton richardsonii was found to be more abundant than noted in previous studies, appearing at many sites and in relatively high density for this species. A similar pattern was noted for Najas flexilis, which was found in high numbers on both the rake toss method and in percent cover observations. It became more apparent on the west shore of the lake as the season progressed. The nuisance invasive Najas guadalupensis is also becoming more abundant throughout the lake. It is now considered “frequently” found in the lake and is likely going to continue to become more abundant. Myriophyllum spicatum was the only invasive species of concern that was found at a lower abundance classification; however, this is may be somewhat misleading. Due to its late growing season, it was not abundant at the time of sampling, though it may have grown more abundant by late summer. Zosterella dubia became the plant with the highest biomass over the course of the survey, carpeting large areas of the lake later in the season. Given its growth form, it is not considered a species of concern in Otsego Lake.

The growing season trends typically followed suit with that described by Harman et al. (1997), with the exception of Z. dubia. That plant grew nearly a month ahead of times reported in earlier years and is reached unprecedented heights for the time of our sampling, having recorded maximum heights up to 1.5-1.75 m in early July. This is likely a combination of a mild preceding winter, increasingly clear lake waters (Waterfield and Albright 2013) and continuously low water levels throughout the summer months. We expect the plant communities to even out as the season continues, with Z. dubia dying back in early November. These variables have potentially altered other plant characteristics, notably P. amplifolius, which was seen growing in more locations than listed in the studies since 1969. In 2012 it was throughout both the northern and southern shores.

Tables 3-5 present data from our PIRTRAM study. As noted in other literature, the PIRTRAM method is excellent for rapid assessment and presence/absence of plant species but typically underestimates the amount of biomass actually present (Harman et al. 2008). We found that the PIRTRAM provided us with accurate presence/absence results and reasonably accurate biomass estimates. The PIRTRAM also served to help us standardize how visual surveys were interpreted regarding relative abundance indicated by the rake toss. Our PIRTRAM data should provide a baseline for future studies on the lake; however, no relative abundance survey has been done previously utilizing this method in Lake Otsego. The percent cover observations logged

from the snorkeling survey expose the relative abundance of each plant species at a particular site. We found that for each snorkeling survey (21 June and 9 July) there were three species that were fairly abundant for that time period. June’s survey resulted in high amounts of C. vulgaris and P. crispus. When the July survey was carried out, V. americana, and Z. dubia were amongst the most common. Both surveys revealed high levels of P. pectinatus for sampling periods, while it became less common as the season progressed.

Of the four invasive nuisance species found in Lake Otsego, P. crispus was notably the most evident during our first sampling period. Anectodotal observations suggest it was considerably more abundant in May before the survey commenced (Albright, 2012b). It formed dense beds in shallow waters and was found growing in waters as deep as 8m. In late June, its beds nearly encircled the entire lake. The plant died down before our second snorkeling survey on 9 July. Najas guadalupensis is not currently considered a problem, but may become a nuisance as it begins to establish itself in Lake Otsego. Myriophyllum spicatum was noted in multiple locations around the lake, but never in high quantities. Nitellopsis obtusa, a macroalgae, has already formed dense beds on the northern shore of the lake and around Sunken Island. We expect this plant to continue to distribute itself more broadly around the lake in the future, eventually reaching the entirety of the lake.

Potamogeton pectinatus and Zosterella dubia were the only plant species we found abundant throughout this survey. Dense beds of P. pectinatus up to 1m tall were formed in Hyde Bay which prevented the growth of most other species. This was the only observed site where such density occurred and, like P. crispus, P. pectinatus died down before our second snorkeling survey on 9 June.

Species that were not specifically noted in this study have gone through no significant changes since the previous 2005 survey. Such species include E. canadensis, P. praelongus, P. illinoensis, M. beckii, R. aquatillus, C. demersum, C. vulgaris, Nitella flexilis, V. americana, and P. zosterformis.

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